DAVID Cameron has urged Vladimir Putin to think carefully about his next moves after the President was granted permission to use military power in Ukraine.

The Prime Minister said there is "no excuse for military intervention" and has called an emergency meeting with the UN security council as the crisis continues to grow.

Mr Cameron said: "Britain views the developments in the Ukraine with growing concern.

"This afternoon, in view of the seriousness of events unfolding there today, and the Russian Parliament's decision to authorise Russian military intervention, the United Kingdom has called an emergency meeting of the UN Security Council.

"There can be no excuse for outside military intervention in Ukraine - a point I made to President Putin when we spoke yesterday.

"Everyone must think carefully about their actions and work to lower, not escalate tensions.

"The world is watching."

His statement comes after the Russian government unanimously voted to support the deployment of Russian troops to the strategic region of Crimea.

Ukraine armed forces are now said to be on "full combat alert".

Foreign Secretary William Hague has said he is "deeply concerned" about this latest turn of events.

He said: "This action is a potentially grave threat to the sovereignty, independence and territorial integrity of Ukraine,

He added he will visit the Ukraine on Sunday and speak directly with the Ukrainian government about the matter.

He said: "I will reiterate the UK's support for the territorial integrity of Ukraine."

Vladimir Putin, right, with former Ukrainian president Viktor Yanukovych [EPA]

Armed men take up positions around the regional parliament building in Crimea [REUTERS]

Russian partners, stop provoking civil and military resistance in Ukraine

Arseny Yatsenyuk

It is believed that around 6,000 troops have been deployed.

Armed men described as Russian troops took control of key airports and a communications centre in on Friday.

Ukraine has accused Russia of a "military invasion and occupation" – raising fears that Moscow is moving to intervene on the strategic peninsula where Russia's Black Sea fleet is based.

The country has urged NATO to protect its borders from aggressive Russian advances.

Ukraine's population is divided in loyalties between Russia and Europe, with much of western Ukraine advocating closer ties with the European Union while eastern and southern regions look to Russia for support.

Crimean's prime minister, Sergei Aksyonov, declared that the armed forces, the police, the national security service and border guards in the region will answer only to his orders.

Ukraine's Prime Minister Arseny Yatsenyuk opened a cabinet meeting in the capital, Kiev, by calling on Russia not to provoke discord in Crimea, a peninsula on the Black Sea.

He said: "We call on the government and authorities of Russia to recall their forces, and to return them to their stations.

"Military intervention would be the beginning of war and the end of any relations between Ukraine and Russia."

President Barack Obama warned Moscow "there will be costs" if it intervenes militarily [REUTERS]

Troops have moved into Belbek Airport [REUTERS]

Meanwhile President Barack Obama warned Moscow "there will be costs" if it intervenes militarily.

But in response, Putin replied Russia has the right to protect its own interests

A statement from the Kremlin reads: "The Russian President underlined that there are real threats to the life and health of Russian citizens and compatriots on Ukrainian territory.

"Vladimir Putin stressed that if violence spread further in the eastern regions of Ukraine and in Crimea, Russia reserves the right to protect its interests and those of Russian speakers living there."

Russia has taken a confrontational stance toward its southern neighbuor after pro-Russian President Viktor Yanukovych fled the country.

Yanukovych was voted out of office by parliament after weeks of protests ended in violence that left over 80 people dead.

Demonstrators sought his resignation after he backed out of signing an agreement to bring Ukraine closer to the European Union instead of Russia.